Researchers who tracked 15,000 children found that babies who can't sit up or crawl at 9 months face falling behind academically compared to those children who could complete these tasks at 9 months old.

The research findings were found by the Millennium Cohort Study, who observed over 18,000 babies born between 2000 and 2001. The study by the University of London, Institute of Education has already published work showing that children from a more affluent background are a year ahead of their poorer classmates when they reach school for the first time.

During the latest study the research team performed a series of simple tests on 9 month old babies to test the early development of their gross and fine motor skills, including large movements like crawling or sitting up (gross motor skill) and picking up an object from the floor between their thumb and finger (fine motor skill).

In these tests 96 percent of 9 month old babies were able to sit up unaided and 92 percent were able to crawl successfully. 69 percent could stand but only 4 percent could take a few steps.

In the fine motor skills test 99 percent of children could pick up an object at 9 months old. Of those 95 percent could pass the object from one hand to another and 89 percent could pick up the object using their thumb and forefinger.

The study group observed that approximately 10 percent of children had what they deemed to be developmental delays and that these delays could affect the progress of children aged 5 years old at school - meaning that they would fall behind compared to their classmates who didn't display these delays at 9 months old.

The researchers, however, did also stress that children are all different and that they develop certain skills at different rates.